Buggy implementation of Lamport's bakery algorithm with deterministic tests.
Created to see vmlens plugin in action.
- Java SDK 1.8
- Maven
$ cd BrokenLamportBakery
$ mvn clean testCheck folder target/interleave for any interleavings which resulted in the failure of the tests.
Each thread, roughly speaking, goes through four fazes.
1. Entering faze [E] - thread picks a ticket
2. Waiting faze [W] - thread waits for others if it needs to do so
3. Critical section [C] - thread enters critical section
4. Unlocking [U] - thread sets ticket to 0
The inserted bug causes threads to not wait for others to finish picking their tickets at the entering faze. Here is a possible scenario were the critical section could be breached.
| Action | Thread 1 | Thread 2 | Notes |
|---|---|---|---|
| 1 | [E] not completed | - | Sees that current max is 0 |
| 2 | - | [E] completed | Gets ticket with number 1 |
| 3 | - | [W] completed | Doesn't wait for Thread 1 to pick ticket |
| 4 | - | [C] not completed | - |
| 5 | [E] completed | - | Gets ticket with number 1 |
| 6 | [W] completed | - | Has lower id so doesn't wait |
| 7 | [C] not completed | Critical section breached | |
| 8 | [U] completed | - | - |
| 9 | - | [U] completed | - |